Verdict
Built from the measurements below
- Accuracy is too close to call: Claude Opus 5.5 scored 85.0% and Gemini 4 Argon 84.8% on the same 80 questions, a gap within what chance alone could produce.
- Gemini 4 Argon is 2.3× cheaper per question as billed ($0.0063 vs $0.015), reasoning tokens included.
- Claude Opus 5.5 generates text 1.9× faster: 129 tokens per second against 69.
- Claude Opus 5.5 starts answering sooner: 2.3 s to the first token, against 3.3 s for Gemini 4 Argon.
Which should you choose?
Choose Claude Opus 5.5 for faster streaming, a quicker first token and more hosts to choose from on OpenRouter (5 against 2). Choose Gemini 4 Argon for the lower cost per correct answer ($0.0074 against $0.017).
Accuracy gap +0.2 points (z = 0.03). We call a winner only when z is at least 1.96, the usual 95% threshold. Speed, latency and price need a 10% margin.